The present application is a request for renewal of an OIG grant initially awarded in 1985. The proposal involves several avenues of research relevant for problems of oncology and general aspects of the control of gene expression in animal cells. Projects include the following: (i) refinement of methods for rapidly identifying most or all of the genes encoded in large pieces of DNA such as might be obtained from yeast artificial chromosomes or from affinity capture of large restriction fragments of genomic DNA, and application of the methods to study of the major histocompatibility complex (MHC), including the hemochromatosis locus; (ii) continuing development of methods for rapidly cloning proteins that activate transcription of particular genes in animal cells, that interact with any particular protein in the milieu of animal cells, or that are associated with particular subcellular structures, and use of these methods to study aspects of the general transcription apparatus, the mechanism of action of tumor suppressor genes, and the regulation of globin gene switching during development; (iii) study of the relationship between translation of exons, exon skipping, and mRNA stabilization and export from the nucleus; and (iv) study of the roles of various regulatory sequences in an MHC Class I gene in the activation of gene expression, the stabilization of active gene expression, and the insulation of the gene from transcriptional effects of adjacent DNA sequences.